#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)n;++i)
#define each(a, b) for(auto (a): (b))
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
#define pb push_back
#define show(x) cout <<#x<<" = "<<(x)<<endl
#define spair(p) cout <<#p<<": "<<p.fi<<" "<<p.se<<endl
#define svec(v) cout<<#v<<":";rep(kbrni,v.size())cout<<" "<<v[kbrni];cout<<endl
#define sset(s) cout<<#s<<":";each(kbrni,s)cout <<" "<<kbrni;cout<<endl

using namespace std;

typedef pair<int,int>P;

const int MAX_N = 100005;

int n,m;
vector<ll> vec;
ll K;

bool possible(int cri)
{
    ll sm = vec[cri] + K;
    int cnt = 0;
    int nw = 0;
    for(int i=n-2;i>=0;i--){
        if(i == cri){
            continue;
        }
        ll hoge = sm - vec[i];
        while(nw < i){
            if(nw == cri){
                nw++;
                continue;
            }
            if(vec[nw] > hoge){
                cnt++;
                nw++;
                if(cnt >= m){
                    return false;
                }
                break;
            }
            nw++;
        }
        if(nw >= i){
            return true;
        }
    }
    return true;
}

int main()
{
    cin >> n >> m;
    cin >> K;
    rep(i,n-1){
        int a;
        cin >> a;
        vec.pb(a);
    }
    if(n == 2){
        cout << vec[0] << endl;
        return 0;
    }
    sort(all(vec));
    int l = 0;
    int h = n-2;
    if(possible(l)){
        cout << vec[0] << endl;
        return 0;
    }
    if(!possible(h)){
        cout << "-1\n";
        return 0;
    }
    while(1){
        int mid = (l+h)/2;
        if(mid == l){
            cout << vec[h] << endl;
            break;
        }
        if(possible(mid)){
            h = mid;
        }else{
            l = mid;
        }
    }
    return 0;
}